1. Field of the Invention
The present invention relates to a method of reacting polyamides, such as nylon 6,6 and nylon 6, with ammonia to obtain a mixture of monomers. The reaction is carried out in the presence of certain Lewis Acid catalyst precursors.
1. Description of the Related Art
Japanese Patent Application Publication 54-84,525 (1979) describes a process for the production of 6-aminocapronitrile (6ACN) and caprolactam (CL) by treating molten polycaproamide (nylon 6) at elevated temperature (340.degree. C.) and pressure (6 kg/cm.sup.2) with ammonia gas.
British Patent 1,172,997 discloses conversion of a polyamide into monomeric compounds by heating the polyamide with ammonia in the presence of hydrogen and a hydrogenation catalyst. Suitable polyamides which may be converted according to the described process include polyhexamethylene adipamide (nylon 6,6) and polycaprolactam (nylon 6). With nylon 6,6, the products obtained are hexamethylenediamine (HMD), hexamethyleneimine, and a small amount of unidentified material. When nylon 6 is reacted in accordance with the process, the resulting products are hexamethylenediamine (HMD), hexamethyleneimine, and N-(6-aminohexyl)-hexamethyleneimine.
Co-pending, co-assigned, U.S. patent application Ser. No. 07/997,612 (Ammonolysis of Nylon), the disclosure of which is hereby incorporated by reference, teaches a nylon ammonolysis process for obtaining a mixture of monomers from nylon 6,6 or a mixture of nylon 6,6 and nylon 6. Monomers obtained from the reaction can be used for reconversion into useful polyamides or for other purposes. The ammonolysis process comprises reacting nylon 6,6 or a mixture of nylon 6,6 and nylon 6, with at least 1 equivalent of ammonia per amide group of the polymer at a temperature between 250.degree. and 400.degree. C. and at a pressure of at least 100 psig, the ratio of nylon 6,6 to nylon 6 in said mixture being from 1:9 to 9:1 on a weight basis.
It has now been found that the ammonolysis process described in the above-mentioned patent application Ser. No. 07/997,612 can be made more efficient when the process is carried out in the presence of certain Lewis acid catalyst precursors.